1. Field of the Invention
This invention relates generally to implantable medical devices, and, more particularly, to methods, apparatus, and systems for using data from a physiological sensor to affect an operation performed by an implantable medical device.
2. Description of the Related Art
There have been many improvements over the last several decades in medical treatments for disorders of the nervous system, such as epilepsy and other motor disorders, and abnormal neural discharge disorders. One of the more recently available treatments involves the application of an electrical signal to reduce various symptoms or effects caused by such neural disorders. For example, electrical signals have been successfully applied at strategic locations in the human body to provide various benefits, including reducing occurrences of seizures and/or improving or ameliorating other conditions. A particular example of such a treatment regimen involves applying an electrical signal to the vagus nerve of the human body to reduce or eliminate epileptic seizures, as described in U.S. Pat. Nos. 4,702,254, 4,867,164, and 5,025,807 to Dr. Jacob Zabara, which are hereby incorporated in their entirety herein by reference in this specification.
Electrical stimulation of the vagus nerve (hereinafter referred to as vagus nerve stimulation therapy) may be provided by implanting an electrical device underneath the skin of a patient and performing a detection and electrical stimulation process. This type of stimulation is generally referred to as “active,” “feedback,” or “triggered” stimulation. Alternatively, the system may operate without a detection system once the patient has been diagnosed with epilepsy, and may periodically apply a series of electrical pulses to the vagus (or other cranial) nerve intermittently throughout the day, or over another predetermined time interval. This type of stimulation is generally referred to as “passive,” “non-feedback,” or “prophylactic,” stimulation. The stimulation may be applied by an implantable medical device that is implanted within the patient's body.
State-of-the-art implantable medical devices generally deliver stimulation signals to one or more regions of a patient's body in a predetermined periodic cycle. Based upon the diagnosed disorder of the patient, a physician may determine a regimen of therapeutic stimulation signals to treat the disorder. The devices then execute the predetermined stimulation regimen. This regimen may be interrupted by predetermined interruption options, such as an external communication from a physician prompting a change in the regimen, a signal from the patient, etc.
The delivery of stimulation may cause physiological variations within a patient's body. However, state-of-the-art implantable medical devices generally do not allow for affecting the predetermined stimulation regimens in response the various physiological variations. Barring active initiation of operational changes prompted by an external source, such as a physician, state-of-the-art implantable devices generally continue a predetermined treatment regimen despite physiological variations. This may cause the implantable medical device to become less responsive to changes in a patient's body.
In an attempt to alleviate some of these problems, designers have provided for altering the regimen based on an external input or input from the patient, for example, through a magnetic signal sent to the implantable device. However, this solution may not be sufficiently reactive to adequately address physiological variations resulting from stimulation regimens. Further, these solutions may require an assessment by an external source, such as a physician or the patient. By the time an external source examines the physiological variations, the patient's body may have gone through further changes, rendering any reaction to the original physiological variation obsolete.
Even though delivery of stimulation may cause specific physiological variations in the body, state-of-the-art implantable devices generally behave independently of such variations, at least in the short term. Long term changes may be provided by re-examination by a physician, i.e. re-diagnosis of a disorder, and then making further adjustments to the stimulation treatment. This may result in significant delay between the physiological changes that may occur due to stimulation, and the time period when manual adjustments to the stimulation regimen is made after examination from a physician. Therefore, efficient and effective reaction to physiological changes may not take place utilizing state-of-the-art implantable devices.
The present invention is directed to overcoming, or at least reducing, the effects of one or more of the problems set forth above.